DESCRIPTION(adapted from applicant?s abstract): The aim of the proposed experiment is to test how the use of tools modifies the neuronal representation of arm position in monkey parietal area 5. The brain contains a representation of the body, and external objects such as tools and prosthetic limbs can be incorporated into this body Image. Many neurons in area 5 respond to the static position of the arm. How are the responses of these neurons modified by the experience of using a tool? First, a neurons sensitivity to arm position will be tested In the dark during a fixation task. Next, the monkey will perform a tool use task in the light requiring him to touch targets with the end of the tool. The tool will be configured to the left of the monkey?s arm. Alter this tool use experience, the neuron?s sensitivity to arm position will be re-tested and the two arm position tuning curves, observed before and after tool use, will be compared. We hypothesize that after the monkey uses the leftward-bent tool, the neuron may begin to encode the offset position of the tool. In this case, the neuron?s tuning curve for arm position should be offset to the right. Neurons will also be tested similarly with a rightward-bent tool. A result of this type would indicate that the tool had been incorporated into the neuronal representation of the body as an extension of the arm. An understanding of how the neuronal representation of the body Image changes with experience may in the future contribute to therapies for stroke patients with parietal damage and amputees with phantom pain.